Poppet valve device and electronic controlled fuel injection apparatus equipped with the device

ABSTRACT

The poppet valve device is composed such that a plurality of axial passages of substantially the same diameter and length communicating to the high-pressure room formed inside the valve seat member between the poppet valve body and the valve seat member are provided in the valve seat member, the passages being located adjacent to each other, or passages being located axially symmetrically, and the annular gap formed between the periphery of the poppet valve body and the inner perimeter of the projecting part on which the valve seat face of the valve seat member is formed is narrow to restrict liquid flow through the annular gap. The electronic controlled fuel injection apparatus equipped with the poppet valve device is composed such that the lower end part of the poppet valve body and the bottom of the valve device accommodating part of the fuel injection apparatus are formed to restrict the flow of the fuel between the lower end of the poppet valve body and the bottom of the valve device accommodation part to the central hollow of the poppet valve body, whereby the occurrence of bouncing is prevented.

This is a divisional of U.S. patent application Ser. No. 11/066,234,filed Feb. 25, 2005.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a poppet valve device for performingopening and closing of a high-pressure liquid passage, specifically to apoppet valve device to control the injection timing of the electroniccontrolled fuel injection apparatus for an internal combustion engine.

2. Description of the Related Art

In diesel engines, electronic controlled fuel injection apparatuses arewidely used recently as effective means for reducing atmosphericpollutant such as NOx(nitrogen oxides) and HC(hydrocarbons) (forexample, see Japanese Laid-Open Patent Application Nos 2001-248479 and2002-98024).

A poppet valve device driven by an electromagnetic valve device is usedin each of these apparatuses for opening and closing the fuel passage inthe apparatus.

FIG. 6 represents an example of a unit injector type electroniccontrolled fuel injection apparatus for diesel engine. The unit injectorlike this is well known in the art and here brief explanation will begiven. In the drawing, reference numeral 100 comprises a fuel injectionpump part 101 and a fuel injection nozzle part 102. The fuel injectionpump part 101 includes a poppet valve 5, and an electromagnetic valvedevice 20 for opening and closing the valve. A plunger 1 fitted into apump case 3 is driven to reciprocate by way of a tappet 6, contact piece7, plunger spring 8, etc. by means of a rocker arm 54 which is drivenmechanically by the engine crank shaft to oscillate. A plunger chamber25 is communicated to the injection nozzle part 102 via a fuel passage052 on one side and communicated to the poppet valve 5 via a fuelpassage 52 on the other side. The fuel passage 52 is communicated ordiscommunicated to a fuel passage 12 connecting to a fuel tank(not shownin the drawing) by opening or closing of the poppet valve 5 which isopened or closed by the electromagnetic valve device 20. The fuelinjection nozzle part 102 includes a fuel injection nozzle 2, and aneedle valve spring 51. The fuel pushed by a plunger 1 to be compressedin the plunger chamber 25 reaches through the fuel passage 052 to a fuelpool 02 and injected from the injection holes 02 a.

When the poppet valve 5 is opened, the pressure in the plunger chamber25 does not increase by a down stroke of the plunger 1 because theplunger chamber 25 is communicated to the fuel tank through the fuelpassage 52, the poppet valve which is opened, and the fuel passage 12.When the poppet valve 5 is closed, the pressure in the plunger chamber25 increases as the plunger 1 moves down, and when the pressure in thefuel pool 02 reaches the needle-opening pressure, the needle valve 4lifts up overcoming the spring force of the needle valve spring 51 andthe fuel begins to be injected from the injection holes 02 a. Duringfuel injection period, the amount of fuel compressed by the plunger islarger than that injected from the injection holes 02 a of the injectionnozzle 2 and the injection pressure increases with time. When the poppetvalve is opened to communicate the plunger chamber 25 to the fuel tank,the pressure in the plunger chamber decreases rapidly, the pressure inthe fuel pool 02 decreases rapidly, the needle valve is pushed down bythe spring force of the needle valve spring 51 for the needle valve tobe closed, and the injection is finished. In the succeeding liftingstroke of the plunger, fuel is sucked into the plunger chamber 25through the fuel passage 12, poppet valve 5 which is opened, and fuelpassage 52.

An example of the conventional poppet valve used in an electroniccontrolled fuel injection apparatus for the purpose as above describedis shown in FIG. 7(A) and FIG. 7(B) together with an electromagneticvalve. FIG. 7(A) shows the state the popped valve is opened, and FIG.7(B) shows the state the poppet valve is closed. In the drawings,reference numeral 20 is an electromagnetic valve device, 3 is the pumpcase of a unit injector as explained above, 52 is a fuel passagecommunicating to the plunger chamber of the unit injector. In theelectromagnetic valve device 20, reference numeral 31 and 16 are valvecases, 031 is a solenoid room inside the valve case 31, 28 is a solenoidaccommodated in the solenoid room 031.

In an armature room 30, an armature 27 is fixed to the top of the poppedvalve 5 by means of a bolt 29.

Reference numeral 10 is a valve seat member and fixed in the pump case 3by means of a fixing screw member 015. Reference numeral 033 is apassage hole drilled in the valve seat member 10 in the radial directionand allows an annular recession 05 of the poppet valve to communicate toan annular recession 17 of valve seat member 10, the recessions 05 and17 being explained later. Reference numeral 5 is a poppet valve which isfit in through-hole of the valve seat member 10 for sliding and to thetop of which is fixed an armature 27 by means of a bolt 29. Referencenumeral 14 is a poppet valve spring disposed between the shoulder partof the poppet valve 5 and the ceiling part of the fixing screw member015. The poppet valve 5 is pushed downward in the direction for thepoppet valve 5 to be opened, that is, in the reverse direction of theattraction force of the armature 27. Reference numeral 05 is an annularrecession formed along the periphery of the poppet valve 5, andreference numeral 17 is an annular recession formed along the peripheryof the valve seat member 10. Reference numeral 12 is a supply and drainpassage, one side thereof communicating to the annular recession 17 andthe other side being connected to a fuel tank(not shown in thedrawings). Reference numeral 10 a is a seat face in the valve seatmember 10, 5 a is a seat face of the poppet valve 5. The seat face 5 aof the poppet valve sits on the seat face 10 a of the valve seat memberwhen closing the poppet valve. According as the seat face 5 a sits on ordeparts from the seat face 10 a of the valve seat member 10, supply anddrain passage 12 is discommunicated or communicated to a fuel passage 52in the pump case 3. Reference numeral 07 is an axial passagecommunicating to an annular recession 06 formed along the insidecircumference of the valve seat member 10, the axial passage 07communicating to the fuel passage 52 which communicates to the plungerchamber of an injection pump not shown in FIG. 7(A), FIG. 7(B). When thepoppet valve 5 is closed, the fuel pressure is high in the recession 06and low in the recession 05.

When electric current is shut off from flowing to the solenoid 28 of theelectromagnetic valve device 20, the poppet valve 5 is pushed down bythe spring force of the poppet valve spring 14, a gap “S” is developedbetween the upper surface of the armature 27 and the lower surface ofthe solenoid 28, the lower end face 5 b of the poppet valve 5 contactsthe bottom face 3 a of the poppet valve device accommodating part of thepump case, the seat face 5 a of the poppet valve 5 departs from the seatface 10 a of the valve seat member 10, and the poppet valve is opened.Therefore, the plunger chamber 25 (see FIG.6) is communicated to thesupply and drain passage 12 through the fuel passage 52, the gap betweenthe seat face 5 a and 10 a developed by the departing of the seat face 5a from the seat face 10 a, the passage hole 033 of the valve seat member10, and the annular recession 17, and the fuel pushed down in theplunger chamber 25 as the plunger 1 (see FIG. 6) moves down is returnedto the fuel tank via the fuel supply and drain pipe 12. Accordingly,fuel is not injected by the down stroke of the plunger 1.

When electric current is flowed to the solenoid 28 of theelectromagnetic valve device 20, the armature 27 and the poppet valve 5connected thereto are lifted up by the attraction generated in thesolenoid 28 against the spring force of the valve seat spring 14 untilthe seat face 5 a of the poppet valve 5 sits on the seat face 10 a ofthe valve seat member 10, and the poppet valve is closed. Then thepressure rises in the plunger chamber 25 as the plunger 1 moves down,and the fuel pushed out from the plunger chamber 25 is injected from theinjection holes 02 a of the injection nozzle 2.

In recent years, injection pressure is increasingly apt to be increasedin order to enhance the effect of an electronic fuel injection apparatusto reduce atmospheric contaminant such as NOx and HC. The poppet valvedevice working in the electronic fuel injection apparatus as describedabove will be brought under severer working condition as fuel injectionpressure increases.

However, with the poppet valve device of prior art, there are problemsthat cavitation erosion occurs in the poppet valve body and valve seatmember due to the outburst of high-pressurized fuel through the gap ofthe valve seat part, that friction of sliding of the poppet valve bodyincreases due to increased side thrust exerting to the poppet valvebody, that a crack occurs in the passage exposed to high-pressure liquidin the valve device and that bouncing occurs when the poppet valveopens, that is, when the seat face of the poppet valve body departs fromthe seat face of the valve seat member and the lower end face of thepoppet valve contacts the bottom face of the poppet valve deviceaccommodating part of the injection pump case.

SUMMARY OF THE INVENTION

The present invention was made in light of the problems as abovedescribed, and the object is to provide a poppet valve device with whichthe occurrence of a crack in the passage exposed to high-pressure liquidin the valve device, occurrence of cavitation erosion in the poppetvalve body and valve seat member of the valve device, increase insliding friction of the poppet valve body, and the occurrence ofbouncing of the poppet valve body can be prevented.

To solve the problems, the present invention proposes a poppet valvedevice for opening and closing a high-pressure liquid passage;comprising a valve seat member and a poppet valve body inserted in thethrough-hole of the valve seat member for sliding, the device beingcomposed such that the sitting of the seat face of the poppet valve bodyonto the seat face of the valve seat member separates an annular,high-pressure room from an annular, low-pressure room, said annularrooms being formed between said poppet valve body and valve seat member,said valve seat member having an axial passage communicating to saidhigh-pressure room and a radial passage communicating to saidlow-pressure room; wherein said axial passage is formed into a pluralityof passages of substantially the same diameter and length locatedadjacent to each other.

In the poppet valve device, the high-pressure room is exposed to highpressure liquid not always but temporarily, and the axial passagecommunicating to the high-pressure room is exposed to repetition of highpressure and low pressure. Conventionally, one axial passage has beenprovided in the valve seat member, and the radial thickness betweenperiphery of the trough-hole (hereafter referred to the sliding surface)and the periphery of the axial passage is inevitably limited for spacelimitation, and when the valve device was used for high-pressureinjection apparatus, the part of said limited radial thickness cracked.

By providing a plurality of axial passages having a required passagearea, the stress due to high pressure in the passages is dispersed andreduced. Therefore, cracks do not occur even if the thickness betweenthe sliding surface and the periphery of the axial passage are the sameas that in the case of conventional one axial passage. Further, as thediameter of each of the passages is reduced, the outer diameter of theannular, high-pressure room can be reduced. As a result, it is possibleto design to reduce the volume of the high-pressure room.

To reduce the volume of high pressure room means that dead volume isreduced, which results in a sharp rise of injection pressure in the caseof a fuel injection apparatus for example. That is, as the rate of riseof the pressure of the fuel compressed by the plunger is less reducedwith smaller dead volume, the injection pressure rises faster with thesame plunger diameter and the same plunger velocity.

Further, in the present invention, it is preferable that said axialpassage is formed into a plurality of passages of substantially samediameter and length located axially symmetrically to the center axis ofthe valve device.

When the valve is closed, the poppet valve body experiences evenpressure around its periphery from the liquid filling the high-pressureroom. When valve is opened, the liquid in the high-pressure room flowsout into the low-pressure room and high-pressure liquid flows into thehigh-pressure room through the axial passage. When one axial passage isprovided, the high-pressure liquid flow entering into the high-pressureroom through the axial passage acts to push the poppet valve body, and aside thrust exerts in the sliding part of the poppet valve body and thethrough-hole of the valve seat member. Therefore, the resistance for thepoppet valve body to slide is caused, which increases with increasedliquid pressure in the axial passage. Further, the flow velocity in theannular gap between the seat faces is faster near the axial passage inthe annular gap and slower at the part opposite to the axial passage.The uneven velocity distribution in the annual gap between the seatfaces induces a decrease in discharge coefficient and increase inpressure loss.

By providing a plurality of axial passages of substantially the samediameter and length located in axial symmetry, the thrusts exerting onthe poppet valve body are balanced because the high-pressure liquidenters into the high-pressure room axially symmetrically, and noresultant thrust exerts on the poppet valve body, as a result poppetvalve body can move smoothly. Further, as a plurality of axial passagesare provided, velocity distribution of flow in the gap between the seatfaces approaches to more even distribution along the annular gap, andmaximum velocity decreases with required flow rate through the gapsecured. By this, the occurrence of cavitation erosion on the poppetvalve body and valve seat member can be suppressed.

In the present invention, it is preferable that the radial width of theannular gap formed between the periphery of said poppet valve body inthe middle part thereof and the inside perimeter of an annularprojection of the valve seat member is narrowed to restrict liquid flowfrom said high-pressure room to said low-pressure room so that theoccurrence of cavitation erosion is suppressed.

When the poppet valve opens, the liquid in the high-pressure room burstsout rapidly to the low-pressure room and cavitation bubbles aregenerated. Cavitation erosion occurs on the surface of the poppet valvebody and valve seat member by the liquid hammer action induced by theextinction of the bubbles.

According to the invention, as the radial width of the annular gapconnecting the high-pressure room to the low-pressure room isrestricted, velocity distribution in the annual gap between the seatfaces is more uniformized resulting in reduced maximum flow velocitywhen the seat face of the poppet valve body departs from the seat faceof the valve seat member and liquid flows out from the high-pressureroom to the low-pressure room passing through the annular gap betweenthe seat faces, and the energy of the liquid flow passing through theannual gap between the seat faces to collide against the poppet valvebody is suppressed, so that the occurrence of cavitation erosion issuppressed.

Further, the present invention proposes an electronic controlled fuelinjection apparatus provided with the poppet valve device, wherein avalve seat member of the poppet valve device is fixed to a valve deviceaccommodating part so that the bottom end of the valve seat member is inclose contact with the bottom face of said valve device accommodatingpart, the poppet valve body of said valve device is forced by an elasticmember in the direction the seat face of said poppet valve body departsfrom the seat face of said valve seat member, and an electromagneticvalve is provided so that the poppet valve is closed when the poppetvalve body is attracted by said electromagnetic valve against theelastic force of said elastic member to allow the seat face of thepoppet valve body to sit on the seat face of the valve seat member andthe poppet valve is opened when the attraction of said electromagneticvalve is released to allow the seat face of the poppet valve body todepart from the seat face of the valve seat member. The electroniccontrolled fuel injection apparatus is characterized by the poppet valvedevice of the invention being mounted with the configuration of valvedevice mounting part the same as is in prior art.

It is preferable that the poppet valve body of the valve device has acentral hollow for allowing the fuel leaked from the sliding part of thepoppet valve body in the trough-hole of the valve seat member to escapeto the poppet valve spring accommodating room, and a cylindricalprojection is formed on the bottom of the valve device accommodatingpart so that the cylindrical projection can fit in the central hollow ofthe poppet valve body with a small radial clearance, whereby the impactwhen the lower end face of the poppet valve body collides against thebottom face of the valve device accommodating part is lessened and theoccurrence of bouncing of the poppet valve body is prevented.

In an electronic fuel injection apparatus, a poppet valve device isprovided for controlling fuel injection timing in the fuel supply lineof the apparatus to supply fuel to the fuel injection pump of theapparatus, and the timing of opening and closing of the valve device iselectronically controlled by means of an electromagnetic valve and anelastic member (usually, a coil spring).

The valve is closed by lifting the poppet valve body by the attractionof the electromagnetic valve and opened by pushing down the poppet valvebody by the spring force of the poppet valve spring until the lower endface of the poppet valve body is brought into contact with the bottomface of the valve device accommodating part of the injection pump case.When the valve is closed, there is formed a clearance between the lowerend face of the poppet valve body and the bottom face of the valvedevice accommodating part, and the clearance is filled with the fuelleaked from the sliding part of the of the poppet valve body in thetrough-hole of the valve seat member, so the fuel in the clearance mustbe exhausted from there in order to allow the lower end face of thepoppet valve body to come into contact with the bottom face of the valvedevice accommodating part.

For this purpose, an escape hole for letting out the fuel to the spacewhere the poppet valve spring is accommodated is provided in the poppetvalve body. By providing a cylindrical projection on the bottom of thevalve device accommodating part to fit into the escape hole with smallradial clearance to form an annular clearance of small radial width whenthe poppet valve body comes down, the fuel in the clearance between thelower end face of the poppet valve body and the bottom face of the valvedevice accommodating part must pass through the annular clearance toescape through the escape hole, by which resistance is caused for thepoppet valve body to move down, and the impact when the lower end faceof the poppet valve body collides against the bottom of the valve deviceaccommodating part is lessened.

If the height of the cylindrical projection is formed to be larger thanthe lift of the poppet valve body, said resistance due to fuel escapeflow restriction acts all over the period the poppet valve body movesdown and if the height is smaller than the lift of the poppet valvebody, said resistance due to fuel escape flow restriction acts justbefore the lower end of the poppet valve body reaches the bottom of thevalve device accommodating part, whereby both good responsibility ofvalve opening and lessening of the impact can be secured, here goodresponsibility means that fuel injection ends sharply.

By softening the impact, valve bouncing that the poppet valve bodycollides against the bottom of the valve device accommodating part andrebounds from the bottom is prevented.

It is required to prevent the bouncing, because the bouncing of thepoppet valve body causes pressure oscillation in the high-pressurepassage between the valve device and the injection nozzle, whichdeteriorates the sharpness of injection end resulting in reduced engineperformance.

In the present invention, it is suitable that the poppet valve body hasa cylindrical projection smaller in diameter than that of the slidingpart thereof at the lower end part thereof, and a cylindrical recess isprovided in the bottom of the valve device accommodating part so thatsaid cylindrical projection can fit into said cylindrical recess of witha small radial clearance to form an annular gap of small radial widthwhen the poppet valve body moves down for opening the valve until thelower end face thereof comes into contact with the bottom face of thevalve device accommodating part, whereby the impact when the lower endface of the poppet valve body collides against the bottom face of thedevice accommodating part is lessened and the occurrence of bouncing ofthe poppet valve body is prevented.

It is also preferable that said poppet valve body is provided with anthrottling member to throttle fuel flow into the central hollow of thepoppet valve body, whereby the impact when the lower end face of thepoppet valve body collides against the bottom face of the deviceaccommodating part is lessened and the occurrence of bouncing of thepoppet valve body is prevented.

In this case, if the throttling hole of the throttling member is formedsuch that the upper (central hollow side) edge thereof is rounded orchamfered and the lower edge is not rounded nor chamfered, the poppetvalve body is easy to move upward and downward movement thereof issuppressed. Therefore, by properly rounding or chamfering the upper edgeof the throttling hole, bouncing when valve closing and when valveopening can be properly controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(A) is a sectional view of a first embodiment of the poppet valvedevice according to the present invention.

FIG. 1(B) is an enlarged detail of part X in FIG. 1A and shown incomparison with the case of prior art.

FIG. 1(C) is a section along line Y-Y in FIG. 1(B) and the case ofpresent invention is compared with the case of prior art.

FIG. 2 is a sectional view of a second embodiment of the poppet valvedevice according to the present invention.

FIG. 3 is a sectional view of a third embodiment of the poppet valvedevice according to the present invention.

FIG. 4(A), FIG. 4(B), and FIG. 4(C) are sectional views of a fourthembodiment and modified embodiments thereof of the poppet valve deviceaccording to the present invention.

FIG. 5 is a graph showing the bouncing of poppet valve.

FIG. 6 is a schematic representation of a unit injector type electronicfuel injection apparatus for a diesel engine.

FIG. 7(A) is a sectional view of a poppet valve device of prior artshowing the state the valve is opened.

FIG. 7(B) is a sectional view of a poppet valve device of prior artshowing the state the valve is closed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will now be detailedwith reference to the accompanying drawings. It is intended, however,that unless particularly specified, dimensions, materials, relativepositions and so forth of the constituent parts in the embodiments shallbe interpreted as illustrative only not as limitative of the scope ofthe present invention.

The First Embodiment

FIG. 1(A) is a sectional view of a first embodiment of the poppet valvedevice according to the present invention, FIG. 1(B) is an enlargeddetail of part X in FIG. 1(A) and shown in comparison with the case ofprior art, and FIG. 1(C) is a section along line Y-Y in FIG. 1(B) andthe case of present invention is compared with the case of prior art.

In FIG. 1(A), a poppet valve device 01 consists of a poppet valve body 5and valve seat member 10. Reference numeral 05 is a low-pressure room,06 is a high-pressure room, 07 is an axial passage connecting to thehigh-pressure room 06, and 033 are radial passages connecting to thelow-pressure room 05. These reference numerals are the same as those ofthe poppet valve device in FIG. 7. Arrows in FIG. 1(B) show the statefuel pressure is exerting in the high-pressure room 06.

In FIG. 1(C), the case the axial passage 07 consists of two passageseach having diameter d₁ is compared with the case the axial passage 07is one passage of diameter of do. The area of two passages of diameterd₁ is equal to the area of one passage of diameter of d₀ in the drawing.In the case of one passage of diameter of d₀, maximum tensile stressoccurs at E, and a crack occurs when the fuel pressure is high in thepassage. In the case of two passages of diameter of d₁, maximum tensilestress occurs at F for each passage, however the tensile stress issmaller, for the diameter of the passage is smaller.

In addition, between the two passages of diameter of d₁, the tensilestress at F is reduced because the circumferential deformation due tothe pressure in the two passages is canceled to each other. As

shown in FIG. 1(B), the diameter D₁ of the annular high-pressure room 06can be reduced when the diameter of the axial passage 07 is d₁ incomparison with the case when the diameter of the axial passage 07 isd₀. Therefore, the volume of the high-pressure room 06 can be reduced.In FIG. 1(B) is shown the case two axial passages are provided, however,above mentioned effect is further enhanced by reducing the diameter ofthe axial passage with increased number of the axial passages.

The Second Embodiment

FIG. 2 is a sectional view of a second embodiment of the poppet valvedevice according to the present invention. In the drawing, two axialpassages 07 of right and left are provided, other than this point thepoppet valve device of FIG. 2 is configured similar to that of FIG. (A),and the same reference numerals are used for components and functionparts same or similar to those of FIG. 1(A). In this case, ashigh-pressure liquid flows into the high-pressure room 06 through theright and left axial passages 07 at the same time, the poppet valve body5 experiences pressure from the high-pressure liquid flow at the sametime from right and left, and the poppet valve body 5 does notexperience a side thrust as does in the case only one axial passage isprovided.

Therefore, the increase of friction by a side thrust when the poppetvalve body slides in the valve seat member 10 can be prevented.

When the valve opens, the liquid in the high-pressure room 06 flows outto the low-pressure room 05 passing through the annular gap developedbetween the seat face 5 a of the poppet valve body 5 and the seat face10 a of the valve seat member 10 as indicated by arrows in FIG. 2.Because high-pressure liquid flows into the high-pressure room 06through the axial passage or passages, liquid flow into the low-pressureroom tends to become strong in the part of the annular gap between theseat faces nearest to the axial passage or passages, and the velocity ofthe flow is largest at that part. As two right and left axial passagesare provided in the case of FIG. 2, the amount of liquid flow per onepassage is halved in comparison with the case only one axial passage isprovided, and the collision energy of the liquid flow impinging againstthe poppet valve body is dispersed in two portions.

Therefore, the occurrence of cavitation erosion is prevented ormoderated. Two right and left axial passages are provided in FIG. 2,however, if a plurality of axial passages more than two are provided inaxial symmetry, the effect is further enhanced.

The Third Embodiment

FIG. 3 is a sectional view of a third embodiment of the poppet valvedevice according to the present invention, and the same referencenumerals are used for components and function parts same or similar tothose of FIG. 1(A). A point different from the poppet valve device ofFIG. 1(A) is that the width “s” of the annular gap between the periphery5 c of the middle part of the poppet valve body 5 and the insideperimeter of the annular projection 10 b of the valve seat member 10 forforming the valve seat 10 a is narrowed to throttle liquid flow.

When the seat face 5 a of the poppet valve body 5 departs from the seat10 a of the valve seat member 10 and a gap is developed between the seatfaces, high-pressure liquid flows out from the high-pressure room 06 tothe low-pressure room 05 passing through the gap between the seat facesand further passing through said annular gap of width “s”. When theannular gap of width “s” is narrowed, the flow through the annular gapis restricted by the narrow annular gap, and flow energy of liquid isalso restricted, so that the collision energy of the liquid flowimpinging against the periphery 5 c of the middle part of the poppetvalve body 5 is also restricted.

Therefore, the occurrence of cavitation erosion is prevented ormoderated. However, if the flow through said annular gap is restrictedexcessively, the velocity of pressure drop of the high-pressure fuel inthe injection pump becomes slower, which results in poor sharpness ofinjection end. Therefore, the width “s” of the annular gap must bedetermined to be not too small.

In the poppet valve devices of prior art, such a consideration as toprovide a throttled part as mentioned above has not been madeheretofore.

The Fourth and Its Modified Embodiments

FIG. 4(A), FIG. 4(B), and FIG. 4(C) show the fourth embodiment and itsmodified embodiments, each gives the similar effect.

In FIG. 4(A) and FIG. 4(B), the poppet valve device is shown in thestate the lower end face of the valve seat member 10 contacts the bottom3 a of the poppet valve device accommodating part of the fuel injectionapparatus. In the drawings, the same reference numerals are used forcomponents and function parts same or similar to those of FIG. 1(A) andexplanation is omitted. Although the lower end part of the poppet valvebody 5 and shape of the bottom face 3 a of the poppet valve deviceaccommodating part is different in each of FIG. 4(A), (B), and (C), thesame reference numerals are used for those for convenience sake.

Generally, bouncing occurs when the poppet valve opens, that is, thepoppet valve body 5 is pushed down by the spring force until the lowerend face 5 b thereof impacts upon the bottom face 3 a of the valvedevice accommodating part and then rebound. The state bouncing isoccurring is shown in FIG. 5. The embodiments of FIG. 4(A) to FIG. 4(C)are configured to prevent the occurrence of bouncing or alleviatebouncing by lessening the impact when the poppet valve body 5 hits thebottom 3 a.

The poppet valve body 5 is provided with a central hollow 115 andlateral holes 116 as shown in FIG. 4(A) to FIG. 4(C) to allow the fuelbetween the lower end face 5 b of the poppet valve body and the bottomface 3 a of the valve device accommodating part to escape through themwhen the poppet valve body 5 moves down and collide on the bottom face 3a. In the embodiment of FIG. 4(A), a cylindrical projection 103 isformed on the bottom 3 a of the valve device accommodating part and thecentral hollow 115 of the poppet valve body 5 is enlarged in diameter atthe lower end part thereof to form an enlarged hole 117 so that thecylindrical projection 103 fits into the enlarged hole 117 with a smallradial clearance to form an annular clearance of small radial width whenthe poppet valve body 5 moves down until the lower end face 5 b comesinto contact with the bottom face 3 a.

Therefore, when the poppet valve body 5 moves down, the fuel between thelower end face 5 b thereof and the bottom face 3 a of the valve deviceaccommodating part escapes toward the central hollow 115 passing throughsaid narrow annular clearance.

Accordingly, there occurs resistance for the poppet valve body to movedown, descending velocity thereof is reduced, and the impact when thelower end face 5 a of the poppet valve body collides on the bottom face3 a of the valve device accommodating part is lessened. The diameter ofthe cylindrical projection 103 and enlarged hole should be determinedsuch that the descending velocity is not excessively reduced. Thevelocity the gap between the valve seat faces increases is reduced bythe reduction in descending velocity of the poppet valve body,therefore, the energy of fuel flow through the gap between the valveseat faces is reduced, which effects to reduce the potential forcavitation erosion.

In the embodiment of FIG. 4(B), a cylindrical recess 104 is formed inthe bottom face 3 a of the valve device accommodating part and acylindrical projection 118 is provided at the lower end part of thepoppet valve body 5 so that the cylindrical projection 118 fits into thecylindrical recess 104 with small radial clearance to form an annulargap of small radial width when the poppet valve body 5 moves down untilthe lower end face 5 b contacts the bottom face 3 a. The work and effectof this embodiment are similar to those of the embodiment of FIG. 4(A).

In the embodiment of FIG. 4(C), an orifice 105 having a small hole 106is attached to the lower end part of the central hole 115 of the poppetvalve body 5, and the work and effect of this embodiment are similar tothose of the embodiment of FIG. 4(A).

As has been described in the foregoing, the poppet valve deviceaccording to the invention can prevent the occurrence of damage in ahigh-pressure liquid passage of the valve device, increase in slidingfriction due to the occurrence of a side thrust, occurrence ofcavitation erosion, and occurrence of bouncing even when the valvedevice is applied to open and close a passage exposed to high-pressureliquid. Particularly, when the valve device is used for an electroniccontrolled fuel injection apparatus, an electronic controlled fuelinjection apparatus superior in durability can be obtained without usingmaterial higher in grade than that used conventionally.

1. A poppet valve device for opening and closing a high-pressure liquidpassage; comprising a valve seat member and a poppet valve body insertedin a through-hole of the valve seat member for sliding, the device beingcomposed such that the sitting of a seat face of the poppet valve bodyonto a seat face of the valve seat member separates an annular,high-pressure room from an annular, low-pressure room, said annularrooms being formed between the poppet valve body and the valve seatmember, said valve seat member having an axial passage communicating tosaid high-pressure room and a radial passage communicating to saidlow-pressure room, said poppet valve body having a central hollow forallowing the liquid to escape outside of the poppet valve body; whereinthe radial width of an annular gap formed between the periphery of saidpoppet valve body in the middle part thereof and the inside perimeter ofan annular projection of the valve seat member is narrowed to restrictliquid flow from said high-pressure room to said low-pressure room sothat the occurrence of cavitation erosion is suppressed.
 2. Anelectronic controlled fuel injection apparatus provided with the poppetvalve device of claim 1, wherein the valve seat member of the poppetvalve device is fixed to a valve device accommodating part so that thebottom end of the valve seat member is in close contact with the bottomface of said valve device accommodating part, the poppet valve body ofsaid valve device is forced by an elastic member in the direction theseat face of said poppet valve body departs from the seat face of saidvalve seat member, and an electromagnetic valve is provided so that thepoppet valve is opened when the poppet valve body is attracted by saidelectromagnetic valve against the elastic force of said elastic memberto allow the seat face of the poppet valve body to sit on the seat faceof the valve seat member and the poppet valve is closed when theattraction of said electromagnetic valve is released to allow the seatface of the poppet valve body to depart from the seat face of the valveseat member.
 3. The electronic controlled fuel injection apparatusaccording to claim 2, wherein the poppet valve body of the valve devicehas a central hollow for allowing the fuel leaked from the sliding partof the poppet valve body in the trough-hole of the valve seat member toescape to the poppet valve spring accommodating room, and a cylindricalprojection is formed on the bottom of the valve device accommodatingpart so that the cylindrical projection can fit in the central hollow ofthe poppet valve body with a small radial clearance, whereby the impactwhen the lower end face of the poppet valve body collides against thebottom face of the device accommodating part is lessened and theoccurrence of bouncing of the poppet valve body is prevented.
 4. Theelectronic controlled fuel injection apparatus according to claim 2,wherein the poppet valve body has a cylindrical projection smaller indiameter than that of the sliding part thereof at the lower end partthereof and a central hollow for allowing the fuel leaked from thesliding part of the poppet valve body in the trough-hole of the valveseat member to escape to the poppet valve spring accommodating room, anda cylindrical recess is provided in the bottom of the valve deviceaccommodating part so that said cylindrical projection of the poppetvalve can fit into said cylindrical recess with a small radialclearance, whereby the impact when the lower end face of the poppetvalve body collides against the bottom face of the valve deviceaccommodating part is lessened and the occurrence of bouncing of thepoppet valve body is prevented.
 5. The electronic controlled fuelinjection apparatus according to claim 2, wherein the poppet valve bodyof the valve device has a central hollow for allowing the fuel leakedfrom the sliding part of the poppet valve body in the trough-hole of thevalve seat member to escape to the poppet valve spring accommodatingroom, and the poppet valve body is provided with a throttling member tothrottle liquid flow into the central hollow of the poppet valve body,whereby the impact when the lower end face of the poppet valve bodycollides against the bottom face of the valve device accommodating partis lessened and the occurrence of bouncing of the poppet valve body isprevented.